This invention relates to a method of producing a resin-molded assembly and a method of producing a double-retaining connector, in which the need for an assembling operation of resin-molded products connected together by pins is obviated, and also a molding process thereof is shortened so as to reduce the production cost.
In a conventional resin-molded connector used for connection of electric wiring, it is a common practice to mold or form elastic retaining piece portions (so called lances) integrally on a housing which retaining piece portions are engaged respectively with connection terminals, inserted into the housing of a resin, thereby preventing the connection terminals from being disengaged.
However, a connector, used in electric wiring of a vehicle, is subjected to vibrations and so on during the travel of the vehicle, and therefore there have been extensively used connectors in which a double-retaining member for locking the engagement condition by the elastic retaining piece portions is added so as to prevent the elastic retaining piece portions from being disengaged respectively from the connection terminals.
FIGS. 1 to 4 shows one conventional double-retaining connector.
This double-retaining connector 1 is disclosed in Japanese Patent Unexamined Publication No. Hei. 5-226025, and comprises a housing body 5 of a generally box-shape having elastic retaining piece portions (lances) 4 formed respectively in terminal receiving holes 2 so as to retain connection terminals 3 inserted respectively into the terminal receiving holes 2, a double-retaining member 7 for locking the engagement condition by the elastic retaining piece portions 4, and hinge bands 8 which connects the double-retaining member 7 to the housing body 5 in such a manner that the double-retaining member 7 can be shifted or moved into a locked condition. This double-retaining connector is formed into an integrally-molded construction, using a synthetic resin. Each of the hinge bands 8 defines a narrow band with high flexibility.
Openings 5a are formed through a relevant outer wall of the housing body 5, and retaining portions 7a, formed at a distal end of the double-retaining member 7, can project through the respective openings 5a into the respective terminal receiving holes 2.
In this double-retaining connector 1, the retaining portions 7a of the double-retaining member 7 are provisionally fixed respectively to the openings 5a in the housing body 5 as shown in FIG. 3, and in this condition, the connection terminals 3 are inserted respectively into the terminal receiving holes 2. Then, as shown in FIG. 4, after the elastic retaining piece portions 4, provided respectively in the terminal receiving holes 2, are engaged respectively with the inserted connection terminals 3, the double-retaining member 7 is further pushed into the housing body 5 to be completely fixed to the housing body 5.
In this completely-fixed condition, the retaining portions 7a of the double-retaining member 7 prevent the connection terminals 3 from rising, thereby locking the retaining condition by the elastic retaining piece portions 4.
In the double-retaining connector 1, the double-retaining member 7 can be molded integrally with the housing body 5 through the flexible hinge bands 8 interconnecting the two members, and the double-retaining member 7 can be freely shifted into the provisionally-fixed condition of FIG. 3 and the completely-fixed condition of FIG. 4.
However, the hinge bands 8 are highly flexible, and therefore have a small force to limit the direction of movement of the double-retaining member 7, and when shifting the double-retaining member 7 into the provisionally-fixed condition of FIG. 3 or the completely-fixed condition of FIG. 4, the operator must suitably control a manipulation force to shift the double-retaining member 7 with the fingers, and therefore there has been encountered a problem that the efficiency of the assembling operation is low.
In addition, when shifting the double-retaining member 7 into the provisionally-fixed condition of FIG. 3 or the completely-fixed condition of FIG. 4, the manipulation force must be controlled so that the double-retaining member 7 can move in a predetermined direction and into a predetermined position, and therefore there is encountered a problem that an automatic assembling operation can not be achieved.
Under the circumstances, there has recently been proposed a double-retaining connector 10 shown in FIGS. 5 to 7.
This double-retaining connector 10 is disclosed in Japanese Patent Unexamined Publication No. Hei. 7-312255, and a housing body 11 made of a resin has terminal receiving holes 2, and engagement pins 11b are provided respectively at opposed right and left outer walls 11a of the housing body 11, and project away from each other.
As shown in FIG. 6, a double-retaining member 12 for retaining connection terminals 3, received respectively in the terminal receiving holes 2, in a double manner has fitting holes 12a (which are fitted respectively on the engagement pins 11a) formed respectively through oppose right and left outer walls 12b thereof, and the double-retaining member 12 is pivotally connected to the housing body 11 by the engagement pins 11b fitted respectively in the fitting holes 12a. 
With this construction in which the housing body 11 and the double-retaining member 12 are connected together by the pins, the direction (path) of movement of the double-retaining member 12 can be limited to a predetermined direction when provisionally or completely fixing the double-retaining member 12 to the housing body 11, and therefore it is not necessary to carefully control a manipulation force to move the double-retaining member 12.
Therefore, after the housing body 11 and the double-retaining member 12 are connected together by the engagement pins 11b, the assembling operation thereafter is very easy, and this alleviates the burden on the operator, and besides the assembling operation can be effected automatically.
In the above double-retaining connector 10, however, when the engagement pins 11b of the housing body 11 are to be fitted respectively into the fitting holes 12a in the double-retaining member 12, those portions of the outer walls 12b, having the fitting holes 12a, must be forcibly urged or moved away from each other, and therefore there has been encountered a problem that considerable time and labor are required for connecting the housing body 11 and the double-retaining member 12 together.
In addition, the outer walls 12b of the double-retaining member 12 must be forcibly deformed elastically when fitting the engagement pins 11b respectively into the fitting holes 12a formed respectively through the outer walls 12b, and therefore the length of projection of the engagement pins 11b cannot be made long, and the depth of fitting of each engagement pin 11b in the fitting hole 12a is small. Therefore, if the outer wall 12b is warped outwardly by a strain after the molding, this fitting engagement can be easily released, and therefore there has been encountered a problem that the strength of connection between the housing body 11 and the double-retaining member 12 cannot be increased.
It is therefore an object of this invention to overcome the above problems, and more specifically to provide a method of producing a resin-molded assembly or a double-retaining connector in which resin-molded products are connected together by pins, and the products can be molded integrally with each other in such an assembled condition that these molded products are connected together by the pins, and therefore the need for an assembling operation of the resin-molded products connected together by the pins is obviated, and also a molding process is shortened so as to reduce the production cost.
The above object has been achieved by a method of producing a resin-molded assembly including a first molded product having engagement pins which are formed respectively on opposite wall surfaces thereof and coaxially projected away from each other, and a second molded product having fitting holes which are formed respectively in opposed walls thereof and are respectively engaged with the engagement pins in such a manner that the second molded project is pivotally or slidably connected to the first molded product by coupling the engagement pins with the fitting holes respectively, the method comprising the steps of:
selecting resin materials used respectively for the molded products in such a manner that a shrinkage coefficient of the first molded product can be higher than that of the second molded product; and
multicolor molding the first and second molded products integrally with each other in an assembled condition so that the first molded product is detachable from the second molded product by elastically deforming at least one of the opposed walls of the second molded product and the opposite walls surfaces of said first molded product to thereby clear the fitting holes from the engagement pins.
The above object has been achieved also by a method of producing a double-retaining connector including:
a resin housing body comprising; terminal-receiving chambers into which terminals connected respectively to ends of wires are inserted, terminal retaining members provided in the terminal receiving chambers for retaining the connection between the terminals and the terminal receiving chambers, and engagement pins which are formed respectively on opposite outer wall surfaces of the housing body and coaxially projected away from each other; and
a resin double-retaining member for locking the retained condition by the terminal retaining members, the double-retaining member having fitting holes which are formed respectively in opposed walls thereof and are fitted respectively on the engagement pins in such a manner that the double-retaining member is pivotally or slidably connected to the housing body by the engagement pins fitted respectively in the fitting holes;
the method comprising the steps of:
selecting resin materials used respectively for the molded products in such a manner that a shrinkage coefficient of the housing body can be higher than that of the double-retaining member; and
multicolor molding the housing body and the double-retaining member integrally with each other in an assembled condition such that the double-retaining member is detachable from the housing body by elastically deforming one of the opposed walls of the double-retaining member and the opposite outer wall surfaces of the housing body to thereby clear the fitting holes from the engagement pins.
Further, the above object has been achieved also by a method of producing a resin-molded assembly including a first resin molded product having engagement pins which are coaxially extended with each other and a second resin molded product having fitting holes into which the engagement pins are respectively inserted in such a manner that the first resin molded product is moved relative to the second resin molded product through engagements between the engagement pins and the fitting holes, the method comprising the steps of:
injecting a second resin into a second molding cavity a shape of which is coincided with the second resin molded product having the fitting holes; and
injecting a first resin, having a shrinkage coefficient higher than that of the second resin, into a second molding cavity a shape of which is coincided with the first resin molded product having the engagement pins, wherein the second molding cavity is defined in combination with a portion containing the fitting hole of the second molding product. The foregoing method is preferably carried out such that the first molded product of the resin molded assembly is detachable from the second molded product by elastically deforming least one of the opposed walls of the second molded product and the opposite outer walls surfaces of the first molded product to thereby clear the fitting holes from the engagement pins.
In the above-mentioned method of producing a resin-molded assembly, it is preferable that the first resin molded product includes a resin housing body which comprises terminal receiving chambers into which terminals connected respectively to ends of wires are inserted, terminal retaining members provided in the terminal receiving chambers for retaining the connection between the terminals and the terminal receiving chambers, and the engagement pins which are formed respectively on opposite outer wall surfaces of the housing body and coaxially projected away from each other; and
that the second resin molded product includes a resin double-retaining member for locking the retained condition by the terminal retaining members, the double-retaining member having the fitting holes which are formed respectively in opposed walls thereof and are fitted respectively on the engagement pins in such a manner that the double-retaining member is pivotally or slidably connected to the housing body by the engagement pins fitted respectively in the fitting holes.
In the method of producing the resin-molded assembly and the method of producing the double-retaining connector according to the present invention, the resin-molded products are molded integrally with each other in the assembled condition by the multicolor molding method in such a form that the two molded products are connected together by the pins. At this time, the resin materials of different shrinkage coefficients are used respectively for the molded products so that the resin-molded product, having the pins, can shrink in a larger amount, and therefore the outer peripheral surface of each engagement pin and the inner peripheral surface of the associated fitting hole, which are in contact with each other at the time of the molding, will not adhere to each other.
Therefore, the relative pivotal movement or the relative sliding movement between the molded products will not be affected, and when the molding process is finished, there is obtained the resin-molded assembly or the double-retaining connector in its assembled condition in which the connection between the molded products by the pins has been completed.
Therefore, any cumbersome assembling operation, such as the operation of connection between the molded products by the pins, is not necessary, and besides a plurality of products can be molded at a time, thus shortening the molding process, and therefore the production cost of the resin-molded assembly or the double-retaining connector can be reduced.